The prevention of electrically generated sparks in many industrial environments is essential for preventing explosions. Electric powered lights can be hazardous in locations such as service stations, coal mines, chemical plants, and similar areas where light is needed but where electric sparks are a potential hazard. In these places special electrical cords, explosion proof sealed containers, and complex safety plugs are required to prevent ignition of flammable substances. The danger of causing explosion of flammable substance lies mainly in the connections, where disconnection of even special plugs can cause sparks. Sparks can also occur if the electrical cables or wires are cut. An industrial area of most concern is coal mines, which have a continual presence of methane gas. Coal mines require lights in corridors and on mining machinery, in transport areas and in special areas for construction or maintenance.
Resonant inductive coupling is also being used in wireless power systems. Resonant inductive coupling is the near field wireless transmission of electrical energy between two magnetically coupled coils that are part of resonant circuits tuned to resonate at the same frequency. A transmitter coil in one device transmits electric power across an intervening space to a resonant receiver coil in another device. Resonant transfer works by making a coil having an oscillating current. This generates an oscillating magnetic field. If a second coil is brought near it, the coil can pick up most of the energy before it is lost. This arrangement of resonant inductive coupling provides a short range of wireless transmission of electric power from one device to another which does not create sparks. However this form of safe wireless transmission is not useful for distances greater than 2 meters. What is needed is a resonant inductive coupling system that will transmit electric power over hundreds of feet and which can provide sufficient electric power to operate motors and lights and other electric devices.